Percutaneous transluminal coronary angioplasty (hereinafter "angioplasty") is a procedure used to treat a stenosis within a body vessel of a human being. A medical catheter having an inflatable balloon attached to a catheter shaft and a guidewire shaft is commonly used during the angioplasty procedure. First, the guidewire shaft and balloon are advanced over a guidewire which is positioned within the body vessel until the balloon is adjacent to the stenosis. Subsequently, the balloon is inflated. This causes the site of the stenosis to compress into the arterial wall and the body vessel to dilate.
In recent years, there has been a continuing effort to improve the performance characteristics of medical catheters. Unfortunately, the design of most existing medical catheters has always involved trading off various performance characteristics. For example, many physicians prefer the guidewire movement/tracking of a guidewire shaft made of high density polyethylene ("HDPE") instead of a guidewire shaft made of Polyether Block Amide ("PEBA"), Polyethylene Terephthalate ("PET"), or Nylon. However, a balloon made of HDPE, in many instances, may not have satisfactory inflation or pressure characteristics. In fact, for some applications, balloons made of PEBA, PET, or Nylon provide superior inflation and pressure characteristics. Because PEBA, PET, and Nylon can not be thermally bonded to HDPE, it is often necessary to use an adhesive to bond a PEBA, PET, or Nylon balloon to a HDPE guidewire shaft. Unfortunately, the adhesive bond at the catheter tip has a relatively large profile, and is relatively stiff. As a result thereof the medical catheter is relatively difficult to maneuver because the catheter tip does not track well in the body vessel.
One attempt to solve this problem involves utilizing the same or thermally compatible materials for the guidewire shaft and the balloon, so that the balloon can be thermally bonded to the guidewire shaft. The thermal bonding results in a high strength, durable, flexible, transitionless, and low profile catheter tip. For example, Guidant, located in Temecula, California, manufactures a medical catheter having a balloon and guidewire shaft which are made of nylon. However, this device is not entirely satisfactory because physicians typically prefer a guidewire shaft made of HDPE.
Another attempt to solve this problem involves the co-extrusion of the guidewire shaft with an inner tube made of HDPE and an outer shell made of nylon. Subsequently, a nylon balloon can be thermally bonded to the nylon outer shell. Unfortunately, the co-extruded guidewire shaft can be more difficult to manufacture and delamination of the co-extruded guidewire shaft may occur.
In light of the above, it is an object of the present invention to provide an improved medical catheter which utilizes a guidewire shaft made of HDPE regardless of the material utilized for the inflatable balloon. Another object of the present invention is to provide a medical catheter having good guidewire movement and tracking, as well as a catheter tip having a low profile, and good strength, flexibility and durability characteristics. Still another object of the present invention is to provide a medical catheter having a distal tail which is thermally bonded and transitionless.